The present invention generally relates to a plasma processing technique. More specifically, the present invention is directed to a plasma processing technique capable of uniformly processing samples.
In semiconductor device manufacturing methods, plasma processing apparatus have been widely used in film forming steps and etching steps. As to these plasma processing apparatus, high-precision processing operations and mass production stabilities are required in correspondence with devices which should be manufactured in very fine manners. On the other hand, diameters of wafers to be processed are being enlarged in view of improvements in productivity. Nowadays, the major wafer diameter becomes 300 mm. In correspondence with large diameters of wafers, higher processing uniformity within planes of wafers is required in these plasma processing apparatus.
A factor which may give the largest influence to the processing uniformity is uniformity of plasma. To control plasma distributions in order to obtain uniform plasma, two different methods have been proposed. That is, as to one method, while two sets, or more sets of high frequency power systems are prepared so as to generate plasma, a ratio of supplying electric power to these high frequency power systems is controlled, and as to the other method, mutual reactions between magnetic fields and electromagnetic waves are employed.
Also, such an idea of a plasma processing apparatus equipped with a plasma monitoring means has been processed. For instance, JP-A-8-167588 describes that while a current is supplied to an auxiliary coil in response to a comparison result between the reference distribution condition and a distribution condition of plasma density acquired from the plasma monitoring means, the plasma contained in a reaction chamber is brought into the reference distribution condition.
Further, JP-A-7-86179 discloses that while emission distributions of plasma are acquired from detection signals of photosensors, supplying of electric power to the respective antennas is controlled in such a manner that the acquired emission distributions may become a uniform distribution.